Simian immunodeficiency virus of chimpanzees (SlVcpz) in now recognized as the immediate precursor to human immunodeficiency virus type 1 (HIV-1), yet remarkably, its prevalence, genetic diversity, natural history of infection and transmission patterns in wild chimpanzee populations is virtually unknown. Studies of natural SIVcpz infections are complicated by the species' highly endangered status and by its geographic location in remote areas of sub-Saharan Africa. We have performed exploratory studies aimed at detecting and characterizing SIVcpz infection in wild-living chimpanzees by non-invasive means. These studies have been successful not only in identifying SIVcpz infection in wild apes (Santiago et al., Science, 2002), but also in validating the non-invasive, urine and fecal based methods for SIVcpz antibody and nucleic acid detection (Santiago et aL, J Virol, 2003; Santiago et aL, J Virol, in press). Thus, we are now positioned to conduct the first systematic molecular epidemiological and natural history survey of SlVcpz in wildliving chimpanzee populations. Based on our preliminary work, we hypothesize that SIVcpz infection will be distributed broadly, but unevenly, among central (P. t. troglodytes) and eastern (P. t. schweinfurthii) chimpanzee communities, and that we will identify west-central African SIVcpz lineages proximate to the current M, N and O groups of HIV-1. To test this hypothesis, we will 1. determine the prevalence and genetic diversity of SIVcpz in wild chimpanzees communities throughout equatorial Africa; 2. molecularly characterize major SIVcpz lineages infecting wild chimpanzee populations; 3. study the natural history of SIVcpz infection in wild chimpanzees; 4. determine whether chimpanzees acquire additional SIV infections through hunting and predation of smaller monkeys; To accomplish this, we have assembled an exceptional group of world-renowned primatologists, conservationists, evolutionary biologists and biomedical scientists. Results from these studies will not only provide essential evidence corroborating the P. t. troglodytes origin of HIV-1, but will address other important questions concerning the natural history and biology of this medically important group of viruses.